What is Ignitable Liquid Residue?
Ignitable liquid residue (ILR) is the evidence left behind at the scene of a fire. ILR represents the portion of an ignitable liquid that did not burn during a fire. ILR is different from an accelerant, which implies intent to start a fire. A scientist will be able to determine if ILR is present based on chemical analysis, while information from the scene can help to determine how that ILR was used or why it might be present at the scene. The simple presence of ILR at the site of an arson investigation does not necessarily mean that the fire was deliberately started.
ILRs that are typically found in structural or wildfire/bushfire arson investigations are primarily petroleum based, such as gasoline, diesel, and lighter fluid. There are many different types of ignitable liquids that may be encountered in arson investigations; however, gasoline is the most common ignitable liquid. Other types of ILRs and their relative prevalence in positive samples are listed in Figure 1, along with a typical example of the chemical fingerprint generated by comprehensive two-dimensional gas chromatography (GC×GC).
ILRs are identified and classified based on their chemical composition, carbon numbers, and boiling point range. The chemical signatures of different ILR types can be seen in the 3D-image plots generated by GC×GC analysis in Figure 2.
What are they used for?
Ignitable liquids have many everyday uses, such as fuel for vehicles or other machinery, cleaning products, painting products, solvents, and many others. ILR provides a fingerprint of the ignitable liquid that may have been used to start a fire. This ILR fingerprint is used to determine the presence or absence of an ignitable liquid and can also be used to determine what type of ignitable liquid was used. Definitive detection of ILR in fire debris can influence guilty and non-guilty verdicts in court proceedings and payments for insurance claims. In certain cases, the ILR fingerprint can be linked to a specific source, such as to a specific gas station, or linked to other evidence collected during the investigation (e.g. jerry can and clothing). Chemistry Matters and its analytical partners have accomplished this by using an advanced analytical technique, comprehensive two-dimensional gas chromatography (GC×GC).
- Legal Sampling
- Chain of Custody
- Study Design
- Data Analysis and Visualization
- Data Wrangling
- Multivariate Statistical Analysis
- Principal Component (PCA); Hierarchical Cluster (HCA)
- Science Communication
- Data Science/Big Data
- GC×GC Analysis
- Chemical Fingerprinting
- Arsonous Wildfires
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Chemistry Matters Consulting Services and Expertise
Deliberately caused fires can cause significant damage to property, to the environment, as well as the potential loss of human and animal life. As long as arson continues to be a major crime, suspicious fire scenes will continue to be investigated. For successful prosecutions to occur, the highest level of scientific expertise is required to interpret the evidence. The Chemistry Matters team is well suited to assist in these endeavours. We have the experience to aid in the proper sample collection and legal chain of custody documentation of evidence at fire scenes to meet litigation scrutiny. We have the litigation experience required for expert witness testimony and are actively involved in arson related research by publishing in peer-reviewed journal articles and presenting at scientific conferences.